The field of the present invention is diaphragm pumps exhibiting a peristaltic motion.
Pumps defining a variable volume chamber by using the space between a pump casing and a diaphragm controlled by a nutating wobble plate have been developed. Reference is made to U.S. Pat. No. 3,058,428 to Gemeinhardt and to U.S. Pat. No. 3,922,119 to Rosenquist. In each instance, a nutating wobble plate driven by a shaft operates to lift away from and then compress against a diaphragm in a wavelike or peristaltic motion. An inlet and an outlet through the pump casing with one-way valves for preventing backflow cooperate with the diaphragm to create an appropriate variable pumping chamber with a peristaltic action.
Such peristaltic pumps place substantial demands on the diaphragms employed. Significant suction and discharge heads contribute to performance and efficiency. Thus, pressure demands in both directions are contemplated on such diaphragms during any single cycle. Complex flexure is also required as the wobble plate nutates. Significant numbers of cycles are required for longevity and economic operation. These demands on the diaphragm are frequently competing. A thin and flexible diaphragm is better able to undergo complex flexure and extended cycling. A thick diaphragm is better able to resist the suction and pressure heads. A thick, more structural diaphragm is also better able to accommodate a tying mechanism by which the diaphragm is held to the wobble plate to draw the diaphragm away from the pump casing during the intake cycle. Stretching and buckling are believed to also significantly impact on the longevity of more rigid diaphragms.